1. Field of the Invention
The present invention relates to an offset detecting circuit for detecting an offset voltage and an output circuit for correcting the offset voltage, and a semiconductor integrated circuit including the output circuit.
2. Description of the Prior Art
A conventional output circuit will be explained with respect to its application to a driving integrated circuit (referred to as IC, hereinafter) incorporated in a liquid crystal display panel, with reference to FIG. 7.
As shown in FIG. 7, the conventional output circuit 60 comprises a sample and hold circuit 62 for holding a potential level of a voltage signal received through an input terminal 61 and outputting the held voltage signal, and an operational amplifier 63 for receiving the output of the sample and hold circuit 62 and outputting the amplified voltage through an output terminal 67. The operational amplifier 63 is a voltage follower circuit such that the output of the sample and hold circuit 62 is received through a non-inversion input terminal 64 thereof and an output side 66 thereof is connected to an inversion terminal 65 thereof.
The output circuit 60 as described above is connected to each line of drive lines of a liquid crystal display panel in order to apply a driving voltage to each drive line.
In general, a single driving IC includes several output circuits, and a plurality of driving ICs are required to drive a single liquid crystal display panel.
In the output circuit as described above, since the voltage level of a voltage signal inputted through the input terminal 61 usually fluctuates in the sample and hold circuit 62 and the operational amplifier 63, a voltage signal outputted through the output terminal 67 usually includes a constant error (e.g. an offset) voltage .DELTA.V with respect to the voltage signal inputted through the input terminal 61.
The offset voltage .DELTA.V differs according to the respective output circuits provided in the same driving IC, and in particular the dispersion is relatively large according to the respective driving ICs.
Accordingly, when the liquid crystal display panel is driven by use of a plurality of driving ICs, the driving voltages applied to the respective operation lines of the liquid crystal display panel differ, thus resulting in a problem in that the brightness on the picture plane of the liquid crystal display panel is not uniform.